UCM6202 and UCM6204 support up to 500 users and 50/75 concurrent calls, UCM6208 supports up to 800 users and 100 concurrent calls, Auto Discovery and Zero Configuration of Grandstream SIP endpoints, Integrated 2/4/8 PSTN trunk FXO ports, 2 analog telephone FXS ports with lifeline capability and up to 50 SIP trunk accounts, Gigabit network ports with Integrates PoE, USB, SD card, Supports up to a 5-level IVR (Interactive Voice Response), Built-in call recordings server; recordings accessible via web user interface, Built-in Call Detail Records (CDR) for tracking phone usage by line, date, etc., Supports multi-language auto-attendant and call queue to efficiently handle incoming calls, Strongest possible security protection using SRTP, TLS and HTTPS encryption, Supports any SIP video endpoint that uses the H.264, H.263 or H.263+ codecs